A GTK2 theme, forked from arc-theme, which gives a uniform look to applications using the Monokai color scheme.
Install the theme cloning this repo (git clone https://github.com/avivace/monokai-gtk) and moving it into /usr/share/themes. You can now enable it system-wide.
You can enable GTK themes only for some applications: launch them in this way: GTK2_RC_FILES=/usr/share/themes/monokai-gtk/gtk-2.0/gtkrc your-application (GTK2) or GTK_THEME=your-theme your-application (GTK3). Change the exec parameter in your desktop launcher to save this preference in your DE.
In these screenshots I'm on debian unstable, KDE Plasma 5.8.4, using Arc Dark as desktop theme. The UI font is Helvetica Neue. The Sublime Text 3 theme is Boxy. Here's the reddit thread on /r/unixporn with more details.